Tubular plastic net-like structure consisting of three crossing layers



1966 s. P. ANDERSON ETAL 3,227,134

TUBULAR PLASTIC NET-LIKE STRUCTURE CONSISTING OF THREE CROSSING LAYERSOriginal Filed Nov. 25, 1960 4 Sheets-Sheet 1 INVENTORS MIMI/V 8. 40M

ATTORNEY ETAL 3,227,184 CIURE CONSISTING LAYERS 4 Sheets-Sheet 2ATTORNEY DERSON -LIKE STR CROSSING S. P. AN

Jan. 4, 1966 TUBULAR PLASTI OF T Original Filed Nov. 25, 1960 1 Q m f WM km 1 y/ \//////Y w m CI'/// /AI Jan. 4,1966 57 P. AN TUBULAR PLASTICNET DERSON ETAL 3,227,184 LIKE STRUCTURE CONSISI'ING THREE CROSSINGLAYERS OF Original Filed Nov. 25, 1960 4 Sheets-Sheet 5 ATTORNEY Jan. 4,1966 s. P. ANDERSON ETAL 3,227,184

TUBULAR PLASTIC NET-LIKE STRUCTURE CONSISTING OF THREE CROSSING LAYERS1960 4 Sheets-Sheet 4 Original Filed Nov. 25,

ATTORNEY PLAS'EHC NET-LIKE STRUCTURE CON- S'IS'liING OF'IHREE. CRGSSINGLAYERS Samuel P. Anderson; Williamsviile, N.Y., and Christian B-.Lundsager, Ashton, Mala, assignors to E. I. du Pont de Nemours andCompany, Wilmington, DelL, a corporation of Delaware Originalapplication Nov. 25, 1960, Self. No. 71,506, now Patent No. 3,163,691,dated Dec. 29; 1964-. Divided and thisapplication Sept. 10, 1964, Ser.No. 395,457

4 Ciaims'. (Cl. 138-125) This invention relates to reinforced plasticnetting, and to a. process and apparatus for making it continuously.This application. is a division of our copending application Serial No.71,506, filed November 25-, 1960, non/Patent No. 3,163,691.

Plastic net bags are being introduced to the trade for packaging variousarticles such as produce and candy bars. A process and apparatus formaking. tubular plastic netting suitable for preparing such bags aredisclosed in Mercer, U18. Patent 2,919,467. For reasons of economy andappearance, it isdesirable in many cases to use netting which, however,is not sufiicientl-y stable to retain bag-like dimensions during andafter filling. For example, the filling. of plastic net bags ofdiamond-shaped mesh is complicated by the tendency of the bags toelongate under' the weight of the contents. This is particularlytroublesome in the filling of bags with onions,

oranges or potatoes. The. resulting package often is in the shape ofalong tube rather than that of a conventional bag or somewhat.rectangular shape;

It is an object of this invention to provide reinforced plastic netting.It is a further object to provide tubular plastic netting reinforced inthe longitudinal direction.

stantinventi'on' which comprises a method? of manufacturing an integralplasticnet-likestructure composed of three layers-ofparallel strands andintegral" intersections thereof which comprises extruding streams ofplastic to form said layers of strands from three adjacent diecarryin-gmembers each having a set of extrusion; orifices cooperative with thoselofeach adjacent member, forming integrally extruded unitaryintersections" between the first and second layers and bet-weenthesecond and third layers of strands by uniting adjacent streams asthey are extruded into unitaryintersection-forming streams,co'nt'iiiu'ing' the extrusion while dividing each intersectionformingstream to form separate strand-forming streams and reuniting saidadjacent streams into further unitary intersectiomforming streams. g

This invention further comprises an apparatus for the extrusion ofplastic net comprising three adjacent diecarrying members A, B andwherein member B is situated intermediate members A and C, the lattermembers having surfaces in contacting relationship with surfaces ofmember B, eachof members A and C having a set of strand-extruding dieswhich open on said surfaces at the extrusion end of said dies, member Bhaving a set of strand extruding dies, each die extending transverselyacross the extrusion end of said member B- and opening onto both itssurfaces at the extrusion end, and means for. moving two of said memberstransverse to the direction of extrusion such that the dies of members Aand C and the dies of member B repeatedly pass in registration.

This invention also comprise's a plastic net-like structure consistingof three crossing. layers, each of which is United States Patent 0 aplurality of parallel homogeneous strands which continuously extend andform intersections with the strands of each adjacent layer periodicallyfor the length of said structure, the strands of adjacent layers beingdivisions of the plastic masses which form the intersections of thestrands.

Preferably, the method and apparatus of this invention produce a tubularnet having the strands of one of its layers of strands being parallel tothe axis of the tubular net itself. In all cases the method andapparatus will produce a net having integrally extruded intersectionsbetween adjacent layers. By this is meant integral intersections betweenthe first layer and the second layer and integral intersections betweenthe second layer and the third layer. Only in the most preferredembodiment, however, will the method and apparatus form nets havingintersections of all three layers at the same points; the apparatus toproduce such netting requires synchronization means to accurately timethe movement of the diecarrying members. Such means are known to thoseskilled in the art.

The plastic netting of this invention is preferably produced by themethod and apparatus of this invention but could be produced by othermeans wherein the intersec tions would not necessarily be integrallyextruded.

The term" register or registration as used herein and in the claimsmeans the juxtapositioning of the die orifices of the respective sets intheir displacement as to coincide or come exactly opposite to oneanother or into partially over-lapping portions, so' that eachregistering pair of die orifices forms a single composite orifice commonto both sets of dies, through which each integral intersection isextruded.

By the term plastic (as used-herein and in the claims) is meant (a) Asynthetic thermoplastic capable of melt or com pression' extrusion in amolten state through dies and settable by a cooling medium on issuancefrom the dies. Suitable thermoplastic materials include polyamid'es orsuperpolyamides, such as nylon; polyesters; polyvinylchloride andcopolymers thereof with vinylacet'ate or vinylid'ene chloride;polyethylene and the like and cellulose acetate; or

(1)) Natural or synthetic rubbers, subsequently vulcanized orcontaining'vulcanizing agents; or

(c) Those thermosetting plastic materials or mixtures thereof withthermoplastic materials, which are capable of extrusion; or

((1) Wet spinnable materials, such as viscose, cupramrnonium celluloseor protein material (e.g., from soya bean), capable of extrusion andsetting by immersion in or spraying with a coagulant as the plasticemerges from the dies.

The invention will now be described Withreference to theattacheddrawings-wherein:

FIG. 1 is a sectional elevation of one form of extrusion apparatusaccording to this invention in which two coaxial annular die-carryingmembes are employed with means for movement and the intermediatedie-carrying member is stationary.

FIG. 2 is a partial elevation view of the intermediate die-carryingmember of FIG. 1.

FIG. 3 is a plan View of the three coaxial die-carrying members in threeparts showing the strand-extruding dies iii-three possible positions.

FIG. 4 is a sectional elevation of another form of extrusion apparatussimilar to FIG. 1 wherein only the outer die-carrying member isstationary.

FIG. 5 is a: sectional elevation of still another form of extrusionapparatus similar to FIGS. 1 and 4 wherein only the inner die-carryingmember is stationary.

FIGS. 6 and 8 are perspective diagrams illustrating the principles ofextrusion of three-layer netting according to this invention.

FIGS. 7, 9 and 10 are partial diagrams of net patterns obtainable by theprocess and apparatus of this invention.

With reference to FIG. 1, a plastic material is fed into inlet 1 bysuitable means and flows down into cavities 1a and 1b. Shaft 2 isequipped for rotation through sprocket 3 and contains inner die-carryingmember 4 at its base. Outer die-carrying member 5 is mounted withinhousing 7. Intermediate die-carrying member 8 is stationary and isfixedly attached to extrusion chamber 9. It has a plu rality of orifices10 which permit flow of the plastic from cavity 1a to cavity 111 anddown around all three die-carrying members. Outer die-carrying member 5is also provided with a sprocket 6 for rotation by suitable means.

FIG. 2 illustrates inner die-carrying member 8 in detail. Slots 12 inits base are the dies which form the intermediate layer of strands.These slots extend further from the face of the dies than the dieportions of members 4 and 5 to enable a plastic feed to the slots fromboth cavities 1a and 1b.

FIG. 3 illustrates the extrusion end of the die-carrying members 4, 5and 8. Outer die-carrying member 5 is shown to contain a plurality ofdies 11 which open onto .its surface of contact with die-carrying member8. Inner die-carrying member 4 is shown to have a plurality of dies 13which open onto its surface of contact with diecarrying member 8.Intermediate die-carrying member 8 is shown having a plurality of slots12 which extend radially across its surface and open onto its surfacesof contact with both die-carrying members 4 and 5.

It should be noted that FIG. 3 is divided into parts I, II and III. PartI shows the dies 11, 12 and 13 out of registration; in this positioneach set extrudes individual strands. In part H, dies 11 and 12 areshown in registration and, therefore, capable of extruding unitaryintersections between two layers, but dies 13 are shown out ofregistration and, therefore, capable only of extruding individualstrands. In part III, all three sets of dies 11, 12 and 13 are shown inregistration and, therefore, capable of extruding unitary intersectionsof all three layers of strands. Synchronization in required to cause theregistration shown in part III at regular intervals. The operation ofthe three die-carrying members illustrated in FIG. 3 is applicable tothe apparatus illustrated in FIGS. 4 and 5 as well as FIG. 1.

FIG. 4 illustrates an apparatus according to this invention similar tothat in FIG. 1 except that in FIG. 4 the outer die-carrying member isstationary and the inner two die-carrying members are rotatable. In thisembodiment,

outer die-carrying member 5 is attached to the housing 7. Theintermediate die-carrying member 8 is rotatable and has sprocket 6connected thereto. Inner diecarrying member 4 is attached to the base ofthe shaft 2 as it was in FIG. 1. Sprocket 3 is also attached to theshaft for the purpose of imparting rotation thereto. Intermediatedie-carrying member 8 also has a plurality of orifices 10 as in FIG. 1to permit a flow of plastic from cavity 1a to cavity 1b.

In FIG. 5, a further modification of the apparatus of this invention isshown wherein the inner die-carrying member 4 is held stationary whilemembers 5 and 8 are rotatable. Another major difference is that in FIG.5, shaft 2 is hollow containing inlet 1 and the plastic is introducedtherethrough flowing out through orifices 21 into cavity 1a.Intermediate die-carrying member 8 also has a plurality of orifices 10therein which permit the plastic to flow from cavity 1a to cavity 1b.Die-carrying members 5 and 8 are equipped with sprockets 6 and 3,respectively to impart rotation.

FIG. 6 illustrates a portion of the die-carrying members according tothis invention which for convenience are shown in rectilinear form.Die-carrying members 31, 32 and 33 have sets of dies 34, and 36 therein,respectively. Layers of strands 34a, 35a and 36a are extruded from dies34, 35 and 36, respectively. In the case illustrated, die-carryingmembers 31 and 33 are moved transversely in opposite directions whileintermediate diecarrying member 32 is held stationary. At the pointwhere dies 34 and 35 are in registration during relative movement,unitary intersections 37 are produced, whereas, when dies 35 and 36 arein registration, unitary intersections 38 are produced. FIG. 7illustrates a portion of a net produced from the dies illustrated inFIG. 6 using corresponding reference numerals.

FIG. 8 illustrates an assembly identical to that in FIG. 6. However, therelative movement of die-carrying members 31, 32 and 33 has beensynchronized such that dies 34 and 36 pass dies 35 simultaneously duringextrusion producing integral intersections 39 composed of all threelayers of strands. This method of operation produces a net shown in FIG.9 wherein all intersections are unitary intersections of all threelayers of strands.

FIG. 10 illustrates a net produced according to the invention whereinone die-carrying member is held stationary to produce longitudinalstrands 36a while the other two die-carrying members are moved in thesame direction but at different rates to produce diagonal strands 34aand 3511.

In the above illustrations, the intermediate die-carrying member hasbeen shown to be stationary. However, either of the die-carrying memberscould be held stationary with relative movement of the remaining twomembers. Thus, the invention embodies nets having the longitudinalstrands lying in any one of three layers.

Although the above apparatus illustrations have been shown to be thosewhich would produce tubular nets, this invention also embodies apparatuswhich would have rectilinear dies such as those shown in FIGS. 6 and 8.Suitable equipment for employing such dies is shown in FIGS. 6 through 8of Mercer, US. Patent 2,919,467 which could be appropriately modified inview of the teachings herein.

The strands produced by this invention may have various cross-sectionalshapes, e.g., square, oval, flat on one side, etc. This is largely amatter of choice of design and may depend upon the particular use towhich the product will be put.

The nets produced according to this invention have greater dimensionalstability and strength. They are particularly useful for use in plasticnet bags wherein retention of shape and dimensions is important. Anotheradvantageous use is in extruded rigid tubes of stiff netting wherein thethird reinforcing layer enables better resistance to compressive radialstress.

What is claimed is:

1. A plastic net-like structure consisting of three crossing layers,each of which is a plurality of parallel homogeneous strands whichcontinuously extend and form intersections with the strands of eachadjacent layer periodically for the length of said structure, thestrands of adjacent layers being divisions of the plastic masses whichform the intersections of the strands.

2. A tubular plastic net-like structure consisting of three concentriccrossing layers, each of which is a plurality of parallel homogeneousstrands which continuously extend and form intersections with thestrands of each adjacent layer periodically for the length of saidstructure, the strands of adjacent layers being divisions of the plasticmasses which form the intersections of the strands, the strands of onelayer being parallel to the axis of the tubular structure and thestrands of the other two layers forming helices about the tubularstructure.

3. Tubular plastic net-like structure according to claim 2 wherein saidintersections consist of the strands of the three layers crossing at thesame points.

4. Tubular plastic net-like structure according to claim 2 wherein saidintersections are integrally extruded unitary intersections.

No references cited.

EARL M. BERGERT, Primary Examiner.

1. A PLASTIC NET-LIKE STRUCTURE CONSISTING OF THREE CROSSING LAYERS,EACH OF WHICH IS A PLURALITY OF PARALLEL HOMOGENEOUS STRANDS WHICHCONTINUOUSLY EXTEND AND FORM INTERSECTIONS WITH THE STRANDS OF EACHADJACENT LAYER PERIODICALLY FOR THE LENGTH OF SAID STRUCTURE, THESTRANDS OF ADJACENT LAYERS BEING DIVISIONS OF THE PLASTIC MASSES WHICHFORM THE INTERSECTIONS OF THE STRANDS.